Electronic device comprising a field effect transistor for high-frequency applications

Abstract

An electronic device comprising a field-effect transistor having an inter digitated structure suitable for high-frequency power applications, and having multiple threshold voltages that are provided in different regions of each a segment of the interdigitated structure. This leads to a dramatic improvement in linearity over a large power range in the back-off region under class AB signal operation.

1. An electronic device comprising a field effect transistor provided with a plurality of parallel-connected transistor segments having mutually different threshold voltages, characterized in that each of the transistor segments comprises a first region and a second region, the first region having a first threshold voltage and the second region having a second threshold voltage. 
     
     
       2. An electronic device as claimed in  claim 1 , characterized in that each of the transistor segments also comprises a third region having a third threshold voltage, which is lower than the second threshold voltage. 
     
     
       3. An electronic device as claimed in  claim 1 , characterized in that the difference between the first and the second threshold voltage amounts to 5-20% of the average threshold voltage. 
     
     
       4. An electronic device as claimed in  claim 2 , characterized in that the difference between the second and the third threshold voltage amounts to 5-20% of the average threshold voltage. 
     
     
       5. An electronic device as claimed in  claim 3 , characterized in that the difference in the threshold voltage amounts to 10-15% of the average threshold voltage. 
     
     
       6. An electronic device as claimed in  claim 2 , characterized in that the first region comprises 40-60% of the surface area of the segment. 
     
     
       7. An electronic device as claimed in  claim 1 , characterized in that the field effect transistor is a MOS transistor, which is defined in a semiconductor body comprising highly doped source and drain zones and a channel region extending between the source zone and the drain zone, with a gate electrode being present which overlaps the channel region upon perpendicular projection thereon, in which the source zone, the drain zone and the gate electrode are connected on the surface to a metal source contact, a drain contact and a gate electrode contact, respectively, in which the semiconductor body comprises a comparatively weakly doped region of a first conductivity type adjoining the surface, which region comprises the highly doped source and drain zone of the opposite, second conductivity type and a weakly doped drain extension between the drain zone and the channel region, in which the gate electrode is electrically insulated from the channel region and in which an electrically insulating layer is laid over the surface, which layer has contact windows above the source zone, the drain zone and the gate electrode, through which contact windows the source zone, the drain zone and the gate electrode, respectively, are connected to the contacts. 
     
     
       8. An electronic device as claimed in  claim 7 , characterized in that another metal strip is present between the gate electrode contact and the drain contact, which strip is electrically insulated from the semiconductor body and which is locally connected to the source strip via an electrical connection, and which form a screen between the gate electrode contact and the drain contact. 
     
     
       9. An electronic device as claimed in  claim 1 , characterized in that the field effect transistor is used as an amplifier and is assembled on a carrier provided with an impedance matching circuit that is connected to the output of the field effect transistor. 
     
     
       10. An electronic device as claimed in  claim 1 , characterized in that the field effect transistor can be operated as an class AB amplifier.